Camshafts which are mounted in sliding bearings have been known for a long time and require no particularly high outlay in terms of design. However, since, for weight-reduction purposes, an ever-increasing number of internal combustion engine parts are made of particularly lightweight materials such as aluminum or even plastic, particular attention must be paid to the transitions between the components made of different materials. In the case of the camshafts, for example, the bearing elements are made of lightweight materials while the camshafts themselves are, as ever, made of steel alloys.
As is known, the lightweight materials have greater expansion coefficients (aluminum: longitudinal expansion coefficient α=23.1*10−6 K−1) than steel alloys, whose longitudinal expansion coefficients are approximately half of this. Indeed, the spatial expansion coefficient γ can even be γ=3*α. Due to these different expansion coefficients of a camshaft which is made of steel and is mounted in a bearing made of aluminum, the bearing play changes as the engine heats up such that the bearing gap increases. As the engine heats up, the increasing bearing gap leads to an accordingly increased oil throughput. In that context, this effect is independent of the design of the bearing, in particular whether this is in the form of a bearing block module or as a conventional mounting in the cylinder head or a guide frame. In that context, it is immaterial whether the bearing channel is split or closed.
DE 10 2012 007 334 A1 discloses a plastic camshaft module as a bearing support, which is cast or injected around separately produced steel bearing rings. However, the bearing rings are not adequately held in the plastic.